Measurement of the Lifetime of the $B_c^{\pm }$ Meson in the Semileptonic Decay Channel

Using approximately $1.3{\mathrm{fb}}^{-1}$ of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the $B_c^{\pm }$ meson in the $B_c^{\pm }\to J/\psi {\mu }^{\pm }+X$ final state. A simultaneous unbinned likelihood fit to the $J/\psi +\mu$ invariant mass and lifetime distributions yields a signal of $881\pm 80(\mathrm{stat})$ candidates and a lifetime measurement of $\tau (B_c^{\pm })={0.448}_{-0.036}^{+0.038}(\mathrm{stat})\pm 0.032(\mathrm{syst})\mathrm{ps}$.

Figure 1

Fit to the mass of the $J/\psi +\mu$ vertex with $J/\psi$ mass sideband (CB) and $B^{+}$ components subtracted and decay length significance $L_{xy}/\sigma (L_{xy})>4$ required.

Figure 2

VPDL distribution of the $J/\psi \mu$ sample with the projected components of the fit overlaid.